Simon Willison Uses Claude Code to Reverse-Engineer LLM Provider HTTP APIs — Designing New Abstraction Layer for LLM Python Library

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Simon Willison released research-llm-apis (April 5), documenting how he used Claude Code to read through Python client libraries for Anthropic, OpenAI, Gemini, and Mistral, then craft raw curl commands testing streaming and non-streaming modes across multiple scenarios. The project supports a major redesign of his LLM Python library's abstraction layer to handle vendor features like server-side tool execution that the current architecture can't support. A practical example of using AI coding agents for API research and architecture design rather than just code generation.